Update only the kernel.

nix/configuration/flake.lock

@@ -178,6 +178,22 @@
         "type": "github"
       }
     },
+    "nixpkgs-kernel": {
+      "locked": {
+        "lastModified": 1778869304,
+        "narHash": "sha256-30sZNZoA1cqF5JNO9fVX+wgiQYjB7HJqqJ4ztCDeBZE=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "d233902339c02a9c334e7e593de68855ad26c4cb",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "d233902339c02a9c334e7e593de68855ad26c4cb",
+        "type": "github"
+      }
+    },
     "nixpkgs-stable": {
       "locked": {
         "lastModified": 1730741070,
@@ -226,7 +242,8 @@
         "disko": "disko",
         "impermanence": "impermanence",
         "lanzaboote": "lanzaboote",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "nixpkgs-kernel": "nixpkgs-kernel"
       }
     },
     "rust-overlay": {

nix/configuration/flake.nix

@@ -20,6 +20,7 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    nixpkgs-kernel.url = "github:NixOS/nixpkgs/d233902339c02a9c334e7e593de68855ad26c4cb";
     lanzaboote = {
       url = "github:nix-community/lanzaboote/v0.4.2";
       inputs.nixpkgs.follows = "nixpkgs";
@@ -34,6 +35,7 @@
     {
       self,
       nixpkgs,
+      nixpkgs-kernel,
       disko,
       impermanence,
       lanzaboote,
@@ -86,6 +88,7 @@
                 nixpkgs.hostPlatform.system = nodeConfig.system;
                 nixpkgs.overlays = [
                   (final: prev: {
+                    kernel = nixpkgs-kernel.legacyPackages."${prev.stdenv.hostPlatform.system}";
                     # stable = nixpkgs-stable.legacyPackages."${prev.stdenv.hostPlatform.system}";
                     unoptimized = import nixpkgs {
                       system = prev.stdenv.hostPlatform.system;

nix/configuration/roles/optimized_build/default.nix

@@ -97,7 +97,7 @@
                   HZ = lib.kernel.freeform "300";
                   HZ_300 = lib.kernel.yes;
                   HZ_1000 = lib.kernel.no;
-                } prev.linux_6_18; # or prev.linux
+                } final.kernel.linux_6_18; # or prev.linux
               }
             )
             (final: prev: {